This invention relates to an improved gear pump and method of making such a pump.
As is well known, gear pumps are widely used for a great variety of purposes. This is due to their ability to generate high pressures. Also these pumps generally have a compact size and shape.
In one commonly utilized type of gear pump there are a pair of intermeshing gears that are supported for rotation about parallel axes. These gears are positioned within a pumping cavity formed by a pump housing. The pump housing cavity has a generally figure 8 shape and is closed by end walls that are in confronting relationship to the flat end faces of the gears. Passages permit the flow of the pumped fluid to and from the space between the gears. Because of machining problems with the prior art type of pumps and their manufacturing methods it has been the practice to interpose bearing end plates between the gear end faces and the pump housing.
For example, published Japanese Patent Application Hei 08-93653 shows a typical prior art pump of this type. The pump main housing member is formed with the pumping chamber by a machining operation through one end face thereof. At the bottom of this cavity, a fillet will be formed of machining necessity. Thus the peripheral edge of the gears must be spaced from this projecting area of the pump housing to avoid interference. This spacing can and is accomplished in part by chamfering the edges of the gear teeth. This however leaves a void area where leakage of the pumped fluid will occur and thus the efficiency of the pump is decreased.
The amount of chamfering required can be reduced by utilizing bearing end plates that engage the flat ends of the gears as shown in FIG. 3 of the noted published Japanese Patent Application. However that adds to the size and cost of the pump. In addition the end plates themselves introduce clearances and areas where leakage can and does occur.
It is, therefore, a principle object of this invention to provide an improved, simplified pump construction and pump manufacturing methodology.
It is a further object of this invention to provide an improved, pump construction and pump manufacturing methodology that offers higher efficiencies and more compact construction than heretofore possible.
In the pumps of this type the gears are supported by gear shafts and at least one of these shafts is driven by some form of prime mover. The gears are expensive to manufacture and are formed from special materials. If they are made integrally with their shafts, as is common practice, the cost increases and the manufacturing can become more difficult. However if the shafts are made separate from the gears, a driving connection must be made to at least the driven gear. This normally is done by a key or pin connection. Those commonly used are costly and troublesome.
It is therefore a further object of this invention to provide a simplified and low cost way of coupling a pump gear and its shaft.